The data come from a series of experiments. To make it easier to describe clearly, we could consider the experiment as having 3 parameters that could be varied. We could call these A, B, and C. A has five levels, B has four levels, and C has three levels. Some combinations of A, B, and C don't go together, so when we remove those we have 42 distinct combinations left.

For each of the 42 combinations, we test the combination of treatment parameters on each of seven subjects to yield a single real number as a result.